Sensor validation

ABSTRACT

An HVAC system includes a compressor, condenser, and evaporator. A sensor measures a value associated with the refrigerant in the condenser or the evaporator, and a controller is communicatively coupled to the compressor and the sensor. The controller determines, based on an operational history the compressor, that pre-requisite criteria are satisfied for entering a sensor validation mode. After determining the pre-requisite criteria are satisfied, an initial sensor measurement value is determined. Following determining the initial sensor measurement value, the compressor is operated according to a sensor-validation mode. Following operating the compressor according to the sensor-validation mode for at least a minimum time, a current sensor measurement value is determined. The controller determines whether validation criteria are satisfied for the current sensor value. In response to determining that the validation criteria are satisfied, the controller determines that the sensor is validated.

TECHNICAL FIELD

The present disclosure relates generally to heating, ventilation, andair conditioning (HVAC) systems and methods of their use. In certainembodiments, the present disclosure relates to sensor validation.

BACKGROUND

Heating, ventilation, and air conditioning (HVAC) systems are used toregulate environmental conditions within an enclosed space. Air iscooled via heat transfer with refrigerant flowing through the HVACsystem and returned to the enclosed space as conditioned air.

SUMMARY OF THE DISCLOSURE

In an embodiment, an HVAC system includes a first compressor circuitwith a compressor, condenser, and evaporator. A sensor is positioned andconfigured to measure a value associated with the refrigerant in thecondenser or the evaporator, and a controller is communicatively coupledto the compressor and the sensor. The controller determines, based on anoperational history the compressor, that pre-requisite criteria aresatisfied for entering a sensor validation mode. The prerequisitecriteria include a requirement that the compressor has been inactive forat least a minimum time. In response to determining the pre-requisitecriteria are satisfied, an initial sensor measurement value isdetermined. Following determining the initial sensor measurement value,the compressor is operated according to a sensor-validation mode.Operating according to the sensor-validation mode involves operating thecompressor at a maximum recommended capacity. Following operating thecompressor according to the sensor-validation mode for at least aminimum time, a current sensor measurement value is determined. Thecontroller determines whether validation criteria are satisfied for thecurrent sensor value, based on a comparison of the current sensormeasurement value to the initial sensor measurement value. In responseto determining that the validation criteria are satisfied, thecontroller determines that the sensor is validated.

HVAC systems may include sensors for monitoring system performance anddetecting system faults. For example, sensors may be positioned tomeasure a saturated suction temperature (or a corresponding saturatedsuction pressure) and a suction temperature of a refrigerant associatedwith an evaporator. This information may be used to determine asuperheat value, the temperature difference between the temperature ofthe superheated vapor refrigerant and the saturation temperature of therefrigerant flowing through an evaporator of an HVAC system. As anotherexample, sensors may be positioned to measure a saturated liquidtemperature (or a corresponding saturated liquid pressure) and a liquidtemperature of refrigerant associated with a compressor. Thisinformation may be used to determine a subcool value, or the temperaturedifference between the saturation temperature of the refrigerant and thetemperature of the subcooled liquid refrigerant flowing through acondenser coil of an HVAC system. The superheat and/or subcool valuesmay be used to detect a loss of charge in an HVAC system and/or diagnoseother system faults. Sensors, such as those described above, may berelied upon to detect system faults and take appropriate correctiveactions. However, there is generally a lack of tools for detectingproblems associated with these sensors and reliably validating theiroperation and the reliability of their measurements.

The unconventional HVAC system and sensor validation approach describedin this disclosure solves problems of previous technology byfacilitating more efficient and reliable sensor validation than waspossible using previous technology. The systems and sensor validationapproach may be particularly effective for HVAC systems with complexconfigurations (e.g., with intertwined condenser coil configurations).This disclosure further encompasses the recognition that it may bedifficult or impossible to validate sensor measurements in systems withmultiple compressor circuits and/or in systems employing intertwinedcoils (e.g., in the condenser and/or evaporator). In some embodiments,multi-level validation checks are performed to further confirm sensorvalidation such that both false positive and false negative sensorfailures are decreased. Certain embodiments may include none, some, orall of the above technical advantages. One or more other technicaladvantages may be readily apparent to one skilled in the art from thefigures, descriptions, and claims included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referenceis now made to the following description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram of an example HVAC system configured for sensorvalidation;

FIG. 2A is a diagram of an example condenser of the HVAC system of FIG.1;

FIG. 2B is a diagram of an example evaporator of the HVAC system of FIG.1

FIGS. 3A-C are diagrams of different coil configurations of theevaporator and/or condenser of the HVAC system of FIG. 1;

FIG. 4 is a flowchart illustrating an example method of validating oneor more sensors of the HVAC system of FIG. 1; and

FIG. 5 is a diagram of the controller of the example HVAC system of FIG.1.

DETAILED DESCRIPTION

Embodiments of the present disclosure and its advantages are bestunderstood by referring to FIGS. 1 through 5 of the drawings, likenumerals being used for like and corresponding parts of the variousdrawings.

As used in the present disclosure, a “saturated liquid” refers to afluid in the liquid state that is in thermodynamic equilibrium with thevapor state of the fluid for a given pressure. A “saturated liquid” issaid to be at the saturation temperature for a given pressure. If thetemperature of a saturated liquid is increased above the saturationtemperature, the saturated liquid generally begins to vaporize. A“superheated vapor” refers to a fluid in the vapor state that is heatedto a temperature that is greater than the saturation temperature of thefluid at a given pressure. A “subcooled liquid” refers to a fluid in theliquid state that is cooled below the saturation temperature of thefluid at a given pressure.

One metric of an HVAC system's operating conditions is the ratio of thecubic feet per meter (CFM) of conditioned air being supplied to a spaceto the tonnage of cooling performed by the system (i.e., or the“CFM/ton” measure of the system). The flow rate of air provided by ablower is generally measured in units of cubic feet per minute (CFM).The tonnage of the HVAC system corresponds to the cooling capacity ofthe system, where one “ton” of cooling corresponds to 12000 Btu/hr. Thetonnage of the HVAC system is largely determined by the speed of thecompressor(s) of the system, such that a decreased compressor speedcorresponds to a decreased tonnage. The relationship between compressorspeed and system tonnage may be approximately linear. Accordingly, theCFM/ton value of an HVAC system may be controlled by adjusting the flowrate of air provided by the blower and/or the speed of thecompressor(s). For example, at a constant air flow rate from the blower,the speed of a variable-speed compressor may be decreased, to increasethe CFM/ton value of the HVAC system.

As described above, prior to the present disclosure, there was a lack oftools for effectively and reliably validating sensors of an HVAC system.As such sensor errors may have gone unreported, resulting in poorefficiency and possible damage to the HVAC system or components thereof.This disclosure particularly encompasses the recognition that one ormore particular criteria (i.e., pre-validation criteria) should be metbefore sensor validation is performed. For example, sensor validationmay only be performed after the HVAC system has been de-energized for atleast a minimum time. The use of these, and other such, pre-validationcriteria ensures that the results of any test(s) used to validate one ormore sensors are repeatable and reliable. In some cases, thepre-validation criteria may instead require that the compression circuitfor which one or more sensors are being validated was inactive for atleast a minimum time. Certain alternative or additional pre-validationcriteria (e.g., a criteria that there is a cooling demand) improvesystem efficiency but limiting the number of validation tests, whichgenerally involve cooling actions of the HVAC system, to times whencooling is actually needed. As demonstrated in various embodimentsdescribed herein, this disclosure further encompasses the uniquerecognition that a multi-tiered validation process may be especiallyeffective at identifying actual sensor errors, thereby limiting falsepositive identification of errors and the resulting cost and down-timeassociated with subsequent maintenance or other intervention.

HVAC System

FIG. 1 is a schematic diagram of an embodiment of an HVAC system 100configured to facilitate effective sensor validation. The HVAC system100 conditions air for delivery to a conditioned space. The conditionedspace may be, for example, a room, a house, an office building, awarehouse, or the like. In some embodiments, the HVAC system 100 is arooftop unit (RTU) that is positioned on the roof of a building and theconditioned air is delivered to the interior of the building. In otherembodiments, portion(s) of the system may be located within the buildingand portion(s) outside the building. The HVAC system 100 may include oneor more heating elements, not shown for convenience and clarity. TheHVAC system 100 may be configured as shown in FIG. 1 or in any othersuitable configuration. For example, the HVAC system 100 may includeadditional components or may omit one or more components shown in FIG.1.

The example HVAC system 100 includes two compression circuits which cangenerally be operated independently. The first compression circuitincludes a first working-fluid conduit subsystem 102 a, at least onecondensing unit 104 a, an expansion valve 122 a, and an evaporator 124a. The second compression circuit includes a second working-fluidconduit subsystem 102 b, at least one condensing unit 104 b, anexpansion valve 122 b, and an evaporator 124 b. The HVAC system 100 alsoincludes a thermostat 154 and a controller 160. The HVAC system 100 isgenerally configured to facilitate validation of sensors 114 a,b, 118a,b, 132 a,b, 136 a,b as described in greater detail below. In brief,validation of one or more of the sensors 114 a,b, 118 a,b, 132 a,b, 136a,b involves measuring an initial value with the sensor(s) 114 a,b, 118a,b, 132 a,b, 136 a,b operating the compressor 106 a,b associated withsensor(s) 114 a,b, 118 a,b, 132 a,b, 136 a,b being validated accordingto a sensor-validation mode (e.g., at 100% compressor 106 a,b capacity)for a brief time (e.g., about 2-10 minutes), taking a second sensormeasurement with the sensor(s) 114 a,b, 118 a,b, 132 a,b, 136 a,b beingvalidated, and comparing the initial sensor measurement to the secondsensor measurement to determine whether the sensor(s) 114 a,b, 118 a,b,132 a,b, 136 a,b are operating correctly and can be validated forfurther use. If one or more of the sensors 114 a,b, 118 a,b, 132 a,b,136 a,b are not validated an alert may be presented (e.g., as alert 158on thermostat 154). In some cases, certain pre-requisite, orpre-validation criteria 162, must be satisfied before sensor validationis performed. Whether the pre-requisite criteria 162 are satisfied maybe based on an operational history of the HVAC system 100 (e.g., howlong one or more of the compressors 1′06 a,b have or have not beenactive).

Each of the working fluid conduit subsystems 102 a,b facilitates themovement of a working fluid (e.g., a refrigerant) through a coolingcycle such that the working fluid flows as illustrated by the dashedarrows in FIG. 1. The working fluid may be any acceptable working fluidincluding, but not limited to, fluorocarbons (e.g. chlorofluorocarbons),ammonia, non-halogenated hydrocarbons (e.g. propane), hydroflurocarbons(e.g. R-410A), or any other suitable type of refrigerant.

Each of the condensing units 104 a,b includes at least one compressor106 a,b, a condenser 108 a,b, and a fan 110 a,b. In some embodiments,one or both of the condensing units 104 a,b is an outdoor unit whileother components of system 100 may be indoors. The compressor 106 a,b iscoupled to the corresponding working-fluid conduit subsystem 102 a,b andcompresses (i.e., increases the pressure of) the working fluid. Thecompressors 106 a,b may be single-speed, variable-speed or multi-stagecompressors. A variable-speed compressor is generally configured tooperate at different speeds to increase the pressure of the workingfluid to keep the working fluid moving along the working-fluid conduitsubsystem 102 a,b. In the variable-speed compressor configuration, thespeed of compressor 106 a,b can be modified to adjust the coolingcapacity of the HVAC system 100. Meanwhile, in the multi-stagecompressor configuration, one or more compressors can be turned on oroff to adjust the cooling capacity of the HVAC system 100.

Each compressor 106 a,b is in signal communication with the controller160 using wired or wireless connection. The controller 160 providescommands or signals to control operation of the compressor 106 a,band/or receives signals from the compressor 106 corresponding to astatus of the compressor 106 a,b. For example, when a compressor 106 a,bis a variable-speed compressor, the controller 160 may provide signalsto control the compressor speed. When a compressor 106 a,b operates as amulti-stage compressor, the signals may correspond to an indication ofwhich compressors to turn on and off to adjust the compressor 106 a,bfor a given cooling capacity. The controller 160 may operate thecompressor 106 in different modes corresponding to load conditions(e.g., the amount of cooling or heating required by the HVAC system100). As described in greater detail below, the controller 160 maydetermine that one or both of the compressors 106 a,b meetspre-validation criteria 162 before the compressor 106 a,b is operated ina validation mode. The controller 160 is described in greater detailbelow with respect to FIG. 7.

Each condenser 108 a,b is configured to facilitate movement of theworking fluid through the corresponding working-fluid conduit subsystem102 a,b. Each condenser 108 a,b is generally located downstream of thecompressor 106 a,b from the corresponding compression circuit and isconfigured to remove heat from the working fluid. Each fan 110 a,b isconfigured to move air 112 a,b across the condenser 108 a,b from thecorresponding compression circuit. For example, a fan 110 a,b may beconfigured to blow outside air through the condenser 108 a,b to helpcool the working fluid flowing therethrough. The compressed, cooledworking fluid flows from the condenser 108 a,b toward an expansiondevice 122 a,b of the corresponding compression circuit.

Each condenser 108 a,b includes a corresponding first sensor 114 ab anda second sensor 118 a,b. In the example of FIG. 1, each first sensor 114a,b may be configured to measure a saturated liquid temperature ofworking fluid flowing in the condenser 108 a,b and provide acorresponding saturated liquid temperature signal (“SLT”) 116 a,b to thecontroller 160. For example, a first sensor 114 a,b may be a temperaturesensor such as a thermocouple or a thermistor. In some embodiments, afirst sensor 114 a,b is a pressure sensor (e.g., to measure a saturationtemperature indirectly via a measure of saturation pressure). Similarly,each second sensor 118 a,b may be configured to measure a liquidtemperature of working fluid flowing in the condenser 108 a,b andprovide a corresponding liquid temperature signal (“LT”) 120 a,b to thecontroller 160. For example, a second sensor 120 a,b may be atemperature sensor such as a thermocouple or a thermistor.

An example of a condenser 108 a,b with sensors 114 a,b and 118 a,b isillustrated in FIG. 2A. As shown in this illustrative example, the firstsensor 114 a,b may be located approximately at the center of the lengthof a circuit of the condenser 108 a,b. This location may correspond to aposition where working fluid flowing through the condenser 108 a,b is asaturated liquid. The second sensor 118 a,b may be located on or near anexit of a subcool circuit of the condenser 108 a,b or on a fluid line(i.e., on or in the working-fluid conduit subsystem 102 a,b) just afterthe outlet of the condenser 108 a,b. Sensors 114 a,b and 118 a,b maygenerally be attached on or within the condenser 108 a,b and/orworking-fluid conduit subsystem 102 a,b using any appropriate means(e.g., clamps, adhesives, or the like).

Referring again to FIG. 1, each expansion device 122 a,b is coupled tothe corresponding working-fluid conduit subsystem 102 a,b downstream ofthe condenser 108 a,b and is configured to remove pressure from theworking fluid. In this way, the working fluid is delivered to theevaporator 124 a,b of the compression circuit and receives heat fromairflow 126 to produce a conditioned airflow 128 that is delivered by aduct subsystem 130 to the conditioned space. In general, an expansiondevice 122 a,b may be a valve such as an expansion valve or a flowcontrol valve (e.g., a thermostatic expansion valve valve) or any othersuitable valve for removing pressure from the working fluid while,optionally, providing control of the rate of flow of the working fluid.An expansion device 122 a,b may be in communication with the controller160 (e.g., via wired and/or wireless communication) to receive controlsignals for opening and/or closing associated valves and/or provide flowmeasurement signals corresponding to the rate of working fluid flowthrough the working fluid subsystem 102 a,b.

The evaporator 124 a,b of each compression circuit is generally any heatexchanger configured to provide heat transfer between air flowingthrough the evaporator 124 a,b (i.e., air contacting an outer surface ofone or more coils of the evaporator 124 a,b) and working fluid passingthrough the interior of the evaporator 124 a,b. For example, theevaporator 124 a,b may be or include one or more evaporator coils, asillustrated in FIG. 2B. In some embodiments, evaporators 124 a,b arecombined in a single coil unit, such as one of the coil units 300, 302,304 illustrated in FIGS. 3A-C. Coil unit 300 of FIG. 3A is in arow-split configuration such that evaporator 124 a is arranged next toevaporator 124 b. Airflow 126 flows first through evaporator 124 abefore flowing through evaporator 124 b and being output as conditionedairflow 128. Coil unit 302 of FIG. 3B is in a face-split configurationsuch that evaporator 124 a is arranged above evaporator 124 b. A portionof airflow 126 flows through evaporator 124 a while a separate portionof airflow 126 flows through evaporator 124 b. Coil unit 304 of FIG. 3Cis in an intertwined configuration such that coils of evaporator 124 aare intertwined with coils of evaporator 124 b. Validation of sensors132 a,b and 136 a,b may be performed differently depending on theconfiguration of evaporators 124 a,b. For instance, when evaporators 124a,b are combined in an intertwined coil configuration as illustrated inthe example of FIG. 3C, pre-validation criteria may indicate that bothcompressors 106 a,b should be off for at least a minimum time before avalidation mode is initiated. Conversely, only the compressor 106 a,bfor which sensor validation is being performed may need to have beende-activated for the minimum time when the face-split configuration ofFIG. 3B is employed.

Referring again to FIG. 1, each evaporator 124 a,b is fluidicallyconnected to the compressor 106 a,b of the corresponding compressioncircuit, such that working fluid generally flows from the evaporator 124a,b to the corresponding condensing unit 104 a,b. A portion of the HVACsystem 100 is configured to move air 126 across the evaporators 124 a,band out of the duct sub-system 130 as conditioned airflow 128. Returnair 140 a,b, which may include outdoor air 140 a, indoor air 140 breturning from the building, or some combination, is pulled into areturn duct 142. A device 141 may be positioned on or in the duct 142and include one or more dampers for modulating the amount of outside air140 a pulled into the return duct 142. When the HVAC system 100 is arooftop unit (RTU), device 141 may be referred to as an economizer. Duct142 may include additional dampers (not illustrated for clarity andconciseness), which may be configured, for example, to adjust the amountof indoor air 140 b pulled into the duct 142.

Each evaporator 124 a,b includes a corresponding third sensor 132 a,band a fourth sensor 136 a,b. In the example of FIG. 1, each third sensor132 a,b may be configured to measure a saturated suction temperature ofworking fluid flowing in the evaporator 124 a,b and provide acorresponding saturated suction temperature signal (“SST”) 134 a,b tothe controller 160. For example, a third sensor 132 a,b may be atemperature sensor such as a thermocouple or a thermistor. In someembodiments, a third sensor 132 a,b is a pressure sensor (e.g., tomeasure a saturation temperature indirectly via a measure of saturationpressure). Similarly, each fourth sensor 136 a,b may be configured tomeasure a suction temperature of working fluid flowing in the evaporator124 a,b and provide a corresponding suction temperature signal (“ST”)138 a,b to the controller 160. For example, a fourth sensor 120 a,b maybe a temperature sensor such as a thermocouple or a thermistor.

An example of an evaporator 124 a,b with sensors 132 a,b and 136 a,b isillustrated in FIG. 2B. As shown in this illustrative example, the thirdsensor 132 a,b may be located approximately on or near an end of adistributor line (e.g., a line from the outlet of the expansion device122 a,b to the inlet of the evaporator 124 a,b). This location maycorrespond to a position where working fluid flowing through, or into,the evaporator 124 a,b is a saturated vapor. The fourth sensor 136 a,bmay be located on or near the outlet of the evaporator 124 a,b. Forinstance, a fourth sensor 136 a,b may be located in a portion of theevaporator 124 a,b containing a super-heated vapor working fluid or on aportion of the working-fluid conduit subsystem 102 a,b leading towardsthe suction side of the compressor 106 a,b. Sensors 132 a,b and 136 a,bmay generally be attached on or within the evaporator 124 a,b and/orworking-fluid conduit subsystem 102 a,b using any appropriate means(e.g., clamps, adhesives, or the like).

A suction side of a blower 144 pulls the return air 140 a,b. The blower144 discharges airflow 126 into a duct 146 such that airflow 126 crossesthe evaporators 124 a,b or heating elements (not shown) to produceconditioned airflow 128. The blower 144 is any mechanism for providing aflow of air through the HVAC system 100. For example, the blower 144 maybe a constant-speed or variable-speed circulation blower or fan.Examples of a variable-speed blower include, but are not limited to,belt-drive blowers controlled by inverters, direct-drive blowers withelectronic commuted motors (ECM), or any other suitable type of blower.The blower 144 is in signal communication with the controller 160 usingany suitable type of wired or wireless connection. The controller 160 isconfigured to provide commands and/or signals to the blower 144 tocontrol its operation (e.g., to adjust the airflow to operate at aprescribed CFM/ton value during a validation mode).

The HVAC system 100 includes one or more sensors 148, 150, 152 in signalcommunication with the controller 160. The sensors 148, 150, 152 mayinclude any suitable type of sensor for measuring air temperature,relative humidity, and/or any other properties of the conditioned space(e.g. a room or building), the HVAC system 100, and/or the surroundingenvironment (e.g., outdoors). The sensors 148, 150, 152 may bepositioned anywhere within the conditioned space, the HVAC system 100,and/or the surrounding environment. For example, as shown in theillustrative example of FIG. 1, the HVAC system 100 may include a sensor150 positioned and configured to measure a return air temperature (e.g.,of airflow 150) and/or a sensor 148 positioned and configured to measurea supply or treated air temperature (e.g., of airflow 128), atemperature of the conditioned space, and/or a relative humidity of theconditioned space. The HVAC system includes a sensor 152 positioned andconfigured to measure an outdoor air temperature and/or other propertiesof the outdoor environment (e.g., relative humidity). In other examples,the HVAC system 100 may include sensors positioned and configured tomeasure any other suitable type of air temperature (e.g., thetemperature of air at one or more locations within the conditionedspace) or other property (e.g., a relative humidity of air at one ormore locations within the conditioned space).

The HVAC system 100 includes a thermostat 154, for example, locatedwithin the conditioned space (e.g. a room or building). The thermostat154 is generally in signal communication with the controller 160 usingany suitable type of wired or wireless connection. The thermostat 154may be a single-stage thermostat, a multi-stage thermostat, or anysuitable type of thermostat. The thermostat 154 is configured to allow auser to input a desired temperature or temperature setpoint 156 of theconditioned space for a designated space or zone such as a room in theconditioned space. The controller 160 may use information from thethermostat 154 such as the temperature setpoint 156 for controlling thecompressors 106 a,b and/or the blower 144. In some embodiments, thethermostat 154 includes a user interface for displaying informationrelated to the operation and/or status of the HVAC system 100, such asone or more alerts 158. For example, the user interface may displayoperational, diagnostic, and/or status messages and provide a visualinterface that allows at least one of an installer, a user, a supportentity, and a service provider to perform actions with respect to theHVAC system 100.

As described in greater detail below, the controller 160 is configuredto perform any of the function described in this disclosure, asdescribed both above and in greater detail below with respect to method400 of FIG. 4. The processor, memory, and interface of the controller160 is described in greater detail below with respect to FIG. 5.

As described above, in certain embodiments, connections between variouscomponents of the HVAC system 100 are wired. For example, conventionalcable and contacts may be used to couple the controller 160 to thevarious components of the HVAC system 100, including, the compressors106 a,b, sensors 114 a,b, 118 a,b, 132 a,b, 136 a,b, the expansionvalves 122 a,b, the blower 144, sensor(s) 148, 150, 152, andthermostat(s) 154. In some embodiments, a wireless connection isemployed to provide at least some of the connections between componentsof the HVAC system 100. In some embodiments, a data bus couples variouscomponents of the HVAC system 100 together such that data iscommunicated therebetween. In a typical embodiment, the data bus mayinclude, for example, any combination of hardware, software embedded ina computer readable medium, or encoded logic incorporated in hardware orotherwise stored (e.g., firmware) to couple components of HVAC system100 to each other. As an example and not by way of limitation, the databus may include an Accelerated Graphics Port (AGP) or other graphicsbus, a Controller Area Network (CAN) bus, a front-side bus (FSB), aHYPERTRANSPORT (HT) interconnect, an INFINIBAND interconnect, alow-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture(MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express(PCI-X) bus, a serial advanced technology attachment (SATA) bus, a VideoElectronics Standards Association local (VLB) bus, or any other suitablebus or a combination of two or more of these. In various embodiments,the data bus may include any number, type, or configuration of databuses, where appropriate. In certain embodiments, one or more data buses(which may each include an address bus and a data bus) may couple thecontroller 160 to other components of the HVAC system 100.

In an example operation of HVAC system 100, the HVAC system 100 startsup to provide cooling to an enclosed space based on temperature setpoint156. For example, in response to the indoor temperature exceeding thetemperature setpoint 156, the controller 160 may cause one or both ofthe compressors 106 a,b and the blower 128 to turn on to startup theHVAC system 100. The HVAC system 100 is generally operated in a normalcooling mode (e.g., associated with a CFM/ton value in a range fromabout 400 to 450 CFM/ton). The controller 160 may intermittently checkwhether pre-requisite criteria 162 are satisfied for entering asensor-validation mode, during which performance of one or more of thesensors 114 a,b, 118 a,b, 132 a,b, 136 a,b is evaluated. Thepre-requisite criteria 162 generally correspond to requirements, basedon the operational history of the HVAC system 100, which ensure sensorvalidation results will be trusted. For instance, the pre-requisitecriteria 162 may include a requirement that a compressor 106 a,bassociated with a sensor 114 a,b, 118 a,b, 132 a,b, 136 a,b to bevalidated has been inactive for at least a minimum time (e.g., for atleast 15 minutes). In this illustrative example, the controller 160determines that sensors 114 a, 118 a, 132 a, 136 a associated with thefirst compressor circuit are due for validation (e.g., because sensors114 b, 118 b, 132 b, 136 b associated with the second compressor circuitwere more recently validated). In this example, sensor 132 a is selectedfor validation.

If the pre-requisite criteria 162 are satisfied for validating sensor132 a, an initial sensor measurement value 163 may be determined usingsignal 134 a. After recording the initial sensor measurement value 164,compressor 106 a associated with (i.e., in the same compressor circuitas) sensor 132 a is operated according to a sensor-validation mode.Operating according to the sensor-validation mode generally correspondsto operating the compressor 106 a at a maximum recommended capacity(e.g., at 100% compressor speed). After the compressor 106 a is operatedaccording to the sensor-validation mode for at least a minimum time(e.g., for 2 minutes), a current sensor measurement value 166 isrecorded based on the current value of signal 134 a. The controller 160then determines whether validation criteria 168 are satisfied based on acomparison of the current sensor measurement value 166 to the initialsensor measurement value 164. For instance, if the difference betweenthe initial 164 and current 166 values (i.e., or the absolute value ofthe difference) is in a predefined acceptable range, the sensor 132 a isconsidered validated, and its continued use is generally accepted.Otherwise, an alert 158 indicated that sensor 132 a needs maintenancemay be provided.

Example Validation Mode Operation

FIG. 4 is a flowchart illustrating an example method 400 of operatingthe HVAC system 100 of FIG. 1. Method 400 may begin at step 402 wherethe controller 160 determines whether one or more of the pre-requisitecriteria 162 are met for entering a sensor validation mode. The sensorvalidation criteria are generally related to the operational history ofthe HVAC system 100 and may include a requirement that the compressor106 a,b has been inactive for at least a minimum time. The minimum timemay correspond to a minimum idle time of at least about 5 minutes to 30minutes. In an embodiment, the minimum time is at least 15 min. For anHVAC system 100 that includes an evaporator 124 a,b that is anintertwined evaporator coil (e.g., as illustrated in FIG. 3C), allcompressors 106 a,b must be inactive for the minimum time in order forthe criteria to be met at step 402. This prevents any inconsistencies insensor measurements caused by cooling between the coils in theintertwined evaporator configuration. Generally, for other evaporatorcoil types (e.g., for face-split configuration 302 of FIG. 3B) thepre-requisite criteria 162 may be that at least the compressor(s) 106a,b corresponding to the circuit of the sensor(s) 114 a,b, 118 a,b, 132a,b, 136 a,b being validated is not active for the minimum time.

In some embodiments, additional or secondary pre-requisite criteria 162are included to further improve the efficiency and/or reliability of thevalidation of method 400. For instance, a secondary pre-requisitecriteria 162 may indicate that there is a cooling demand in the spacebeing conditioned by the HVAC system 100. This may prevent a waste ofenergy when the system 100 is operated according to thesensor-validation mode (i.e., when one or more of the compressors 106a,b are operated at high capacity). In this way, in cooling achievedduring the validation is not wasted. This results in improved overalloperating efficiency of the HVAC system 100. Another example of asecondary pre-requisite criteria 162 is a requirement that the currenttime is an off-peak time (e.g., a time when people are not expected tobe in the space being conditioned by the HVAC system 100) such thatcomfort is not sacrificed during sensor validation. For example, sensorvalidation may only be conducted between midnight and 4 am. Yet furtherexamples of secondary pre-requisite criteria 162 are requirements thatthe outdoor air temp (e.g., measured with sensor 152 of FIG. 1) isgreater than 55° F. and/or that both an outdoor air temperature sensor152 and a return air temperature sensor 150 are operating properly(e.g., providing measurements within expected temperature ranges).

In some cases, the pre-requisite criteria 162 may take into accountwhether previous validations have already been attempted and failed fora given sensor 114 a,b, 118 a,b, 132 a,b, 136 a,b or correspondingcompressor circuit. For instance, a criteria 162 may indicate that asensor-validation mode can only be entered as long as there are lessthan a threshold number of previous failed validation attempts (e.g.,less than two failed validations) since the previous passed validationfor the sensor(s) 114 a,b, 118 a,b, 132 a,b, 136 a,b. In some cases, afurther criteria 162 may include a requirement that the HVAC system 100has no dehumidification demand before entering a sensor-validation mode.If the criteria 162 are not met at step 402, the controller 160generally waits some time interval before repeating step 402 to checkwhether conditions have changed and the criteria 162 are satisfied atstep 402. If the pre-requisite criteria are satisfied at step 402, thecontroller 160 proceeds to step 404.

At step 404, the controller 160 determines which sensor(s) 114 a,b, 118a,b, 132 a,b, 136 a,b should be validated. For instance, the controller160 may determine which compressor circuit is due for sensor validation(e.g., which sensors 114 a,b, 118 a,b, 132 a,b, 136 a,b have gone thelongest time since their last validation). For instance, the controller160 may determine that one or more of sensors 114 a, 118 a, 132 a, 136 afor the first compressor circuit should be validated or that one or moreof sensors 114 b, 118 b, 132 b, 136 b of the second compressor circuitshould be validated. Once one or more sensors 114 a,b, 118 a,b, 132 a,b,136 a,b are identified for validation, one or more initial sensormeasurements are determined at step 406. For example, temperature,pressure, humidity, and/or the like measurements generated by one ormore of the sensors 114 a,b, 118 a,b, 132 a,b, 136 a,b may be receivedby the controller 160. For example, the initial sensor measurements 164may correspond to one or more of the signals 116 a,b, 120 a,b, 134 a,b,138 a,b being received from the corresponding sensors 114 a,b, 118 a,b,132 a,b, 136 a,b. These initial sensor measurements 164 may be stored inmemory (e.g., memory 504 of controller 160 described below with respectto FIG. 5).

At step 408, the compressor(s) associated with the sensor(s) 114 a,b,118 a,b, 132 a,b, 136 a,b being validated (i.e., the sensor(s)determined at step 404) are operated according to a sensor-validationmode. The sensor-validation mode generally corresponds to operationunder high cooling conditions, such that a predefined amount of coolingis achieved and such that subsequently recorded sensor measurements canbe compared to expected measurement values. In some cases, only onecompressor 106 a,b is operating during the sensor-validation mode (i.e.,only the compressor associated with the compression circuit of thesensor(s) 114 a,b, 118 a,b, 132 a,b, 136 a,b being validated). Thesensor-validation mode may correspond to operation at 100% compressorspeed (i.e., at a maximum recommended compressor speed).

In some embodiments, the controller 160 may adjust the CFM/ton settingof the HVAC system 100 to provide greater cooling for the validation.Accordingly, the controller 160 may over-ride a default CFM/ton settingof the HVAC system 100 (e.g., a default value near 400 CFM/ton, e.g.,from about 400 to 450 CFM/ton) to achieve the high cooling conditionsfor the sensor-validation mode. The adjusted CFM/ton setting maycorrespond to operation at a CFM/ton that is less than or equal to about200 CFM/ton. Such a decreased CFM/ton may be achieved by operating at100% compressor speed and a decreased speed of the blower 144 of FIG. 1.Such a decreased CFM/ton may facilitate a more rapid and/or a largermagnitude change in the saturated suction temperature and suctiontemperature measurements (e.g., based on signals 134 a,b and 138 a,b)during operation in the sensor-validation mode, thereby furtherimproving reliability of the results of the sensor validation. In someembodiments, operation in the sensor-validation mode at step 408 mayalso or alternatively involve decreasing the speed of the outdoor fan110 a,b associated with the compression circuit of the sensor(s) 114a,b, 118 a,b, 132 a,b, 136 a,b being validated. Decreasing the speed offan 110 a,b decreases the rate of air flow 112 a,b across the condenser108 a,b. Such a decreased rate of air flow 112 a,b may facilitate a morerapid and/or a larger magnitude change in the saturated liquidtemperature and liquid temperature measurements (e.g., based on signals116 a,b and 120 a,b) during operation in the sensor-validation mode,thereby further improving reliability of the results of the sensorvalidation.

In some embodiments, operation in the sensor-validation mode at step 408may also or alternatively involve closing dampers of the economizer 141(i.e., to prevent outdoor air flow 140 a from entering duct 142). Withthe economizer in the closed position, outdoor air flow 140 a is notprovided across the evaporator 124 a,b. This may facilitate morereliable changes in the saturated suction temperature (e.g., based onsignal 134 a,b) and suction temperature (e.g., based on signal 138 a,b)during operation in the sensor-validation mode, thereby furtherimproving performance of the sensor validation.

At step 410, a delay timer is started. The delay timer runs for theamount of time during which the compressor(s) 106 a,b are operatedaccording to the sensor-validation mode. As an example, the time of thedelay timer may be between 1 and 5 minutes, although any otherappropriate time may be used for the delay timer. In some embodiments,the delay timer runs for 3 minutes before it is complete. At step 412,the controller 160 determine whether the delay timer is complete. If thedelay timer is not complete, the controller 160 continues to wait forthe delay timer to complete. Otherwise, if the delay timer is complete,the controller 160 proceeds to step 414.

At step 414, current sensor measurements 166 are determined. Forexample, temperature, pressure, humidity, and/or the like measurementsgenerated by one or more of the sensors 114 a,b, 118 a,b, 132 a,b, 136a,b may be received by the controller 160 as current measurements 166.For example, the current sensor measurements 166 may correspond to oneor more of the signals 116 a,b, 120 a,b, 134 a,b, 138 a,b being receivedfrom the corresponding sensors 114 a,b, 118 a,b, 132 a,b, 136 a,b. Thesecurrent sensor measurements 166 may be stored in memory for comparisonto the initial sensor measurements 164 (e.g., in memory 504 ofcontroller 160 described below with respect to FIG. 5).

At step 416, the controller 160 determine whether one or more firstvalidation criteria 168 are satisfied. The first validation criteria 168may correspond to a requirement that a current sensor measurement value166 is within an expected range of values or within a predeterminedoffset from an expected value. The first validation criteria 168 maycorrespond to a requirement that a difference between the currentmeasurement value 166 and the initial measurement value 164 for a givensensor 114 a,b, 118 a,b, 132 a,b, 136 a,b is within a predefined rangeof difference values. The predefined range of difference values may bespecific to a particular sensor 114 a,b, 118 a,b, 132 a,b, 136 a,b orsensor type being validated, specific to the HVAC system 100, and/or tothe HVAC system's operating environment (e.g., whether the environmentis associated with a dry climate, cold climate, etc.). As such, thepredefined range of difference values may have been previouslydetermined for the sensor(s) 114 a,b, 118 a,b, 132 a,b, 136 a,b beingvalidated.

For instance, for sensors 114 a,b positioned and configured to measure asaturated liquid temperature of condensers 108 a,b (and providecorresponding SLT signals 116 a,b), the predefined range of differencevalues may be about 5° F. to about 20° F. (e.g., or about 10° F.). Forsensors 118 a,b positioned and configured to measure a liquidtemperature of condensers 108 a,b (and provide corresponding LT signals120 a,b), the predefined range of difference values may be about 0° F.to about 20° F. (e.g., or about 5° F.). For sensors 132 a,b positionedand configured to measure a saturated suction temperature of evaporators124 a,b (and provide corresponding SST signals 134 a,b), the predefinedrange of difference values may be about 5° F. to about 20° F. (e.g., orabout 10° F.). For sensors 136 a,b positioned and configured to measurea suction temperature of evaporators 124 a,b (and provide correspondingST signals 138 a,b), the predefined range of difference values may beabout 5° F. to about 20° F. (e.g., or about 10° F.).

If the first validation criteria 168 not satisfied, an alert may be sentat step 418. For example, an alert may be transmitted to the thermostat154 and displayed on thermostat as alert 158. The controller 160 mayproceed to step 424 to update the validation history for the sensors 114a,b, 118 a,b, 132 a,b, 136 a,b for which validation failed (e.g., toimprove decision making about which sensors 114 a,b, 118 a,b, 132 a,b,136 a,b to subsequently validate at step 404). If the first criteria 168are satisfied, the controller 160 generally proceeds to step 420.

In some embodiments, an optional step 420 is performed where thecontroller 160 determines whether one or more secondary validationcriteria 168 are satisfied. In some embodiments, the secondaryvalidation criteria 168 are not associated with a comparison of aninitial measurement value 164 to a current measurement value 166. Forinstance, the secondary validation criteria 168 may be associated with arequirement that an outdoor temperature (e.g., measured with sensor 152of FIG. 1) is within a first predetermined temperature range and arequirement that a return air temperature (e.g., measured with sensor150 of FIG. 1) is within a second predetermined temperature range. Ifthe secondary criteria 168 are not satisfied at step 420, an alert maybe sent at step 418. For example, an alert may be transmitted to thethermostat 154 and displayed on thermostat as alert 158. The controller160 may proceed to step 424 to update the validation history for thesensors 114 a,b, 118 a,b, 132 a,b, 136 a,b for which validation failed(e.g., to improve decision making about which sensors 114 a,b, 118 a,b,132 a,b, 136 a,b to subsequently validate at step 404). If the firstcriteria 168 are satisfied, the controller 160 generally proceeds tostep 422.

In some embodiments, the controller 160 may determine whether signals116 a,b, 120 a,b, 134 a,b, 138 a,b from each of the sensors 114 a,b, 118a,b, 132 a,b, 136 a,b (e.g., or each of at least two of the sensors 114a,b, 118 a,b, 132 a,b, 136 a,b being validated) did not exhibit asubstantial change during operation in the validation mode. For example,the controller may determine whether the changes in signals 116 a,b, 120a,b, 134 a,b, 138 a,b from all four of the sensors 114 a,b, 118 a,b, 132a,b, 136 a,b being validated for a given compression circuit is greaterthan a threshold value. If the signals 116 a,b, 120 a,b, 134 a,b, 138a,b did not change substantial during validation (e.g., if signals 116a,b, 120 a,b, 134 a,b, 138 a,b changed by less than the thresholdvalue), the controller 160 may determine that the compressor 106 a,b ofthe circuit for which the sensors 114 a,b, 118 a,b, 132 a,b, 136 a,b arebeing validated is malfunctioning. An alert 158 may be provided to thethermostat 154 to indicate such a compressor malfunction.

If the first criteria 168 are satisfied at step 416 (and optionally ifthe secondary criteria 168 are also satisfied at step 420), thecontroller 160 determines that the sensors 114 a,b, 118 a,b, 132 a,b,136 a,b are validated for the compressor circuit at step 422. Thecontroller 160 may proceed to step 422 to update the validation historyfor the sensors 114 a,b, 118 a,b, 132 a,b, 136 a,b at step 424 for whichvalidation succeeded (e.g., to improve decision making about whichsensors 114 a,b, 118 a,b, 132 a,b, 136 a,b to subsequently validate atstep 404).

Modifications, additions, or omissions may be made to method 400depicted in FIG. 4. Method 400 may include more, fewer, or other steps.For example, steps may be performed in parallel or in any suitableorder. While at times discussed as controller 160, HVAC system 100, orcomponents thereof performing the steps, any suitable HVAC system orcomponents of an HVAC system may perform one or more steps of themethod.

Example Controller

FIG. 5 is a schematic diagram of an embodiment of the controller 160.The controller 160 includes a processor 502, a memory 504, and aninput/output (I/O) interface 506.

The processor 502 includes one or more processors operably coupled tothe memory 504. The processor 502 is any electronic circuitry including,but not limited to, state machines, one or more central processing unit(CPU) chips, logic units, cores (e.g. a multi-core processor),field-programmable gate array (FPGAs), application specific integratedcircuits (ASICs), or digital signal processors (DSPs) thatcommunicatively couples to memory 504 and controls the operation of HVACsystem 100. The processor 502 may be a programmable logic device, amicrocontroller, a microprocessor, or any suitable combination of thepreceding. The processor 502 is communicatively coupled to and in signalcommunication with the memory 504. The one or more processors areconfigured to process data and may be implemented in hardware orsoftware. For example, the processor 502 may be 8-bit, 16-bit, 32-bit,64-bit or of any other suitable architecture. The processor 502 mayinclude an arithmetic logic unit (ALU) for performing arithmetic andlogic operations, processor registers that supply operands to the ALUand store the results of ALU operations, and a control unit that fetchesinstructions from memory 504 and executes them by directing thecoordinated operations of the ALU, registers, and other components. Theprocessor may include other hardware and software that operates toprocess information, control the HVAC system 100, and perform any of thefunctions described herein (e.g., with respect to FIG. 4). The processor502 is not limited to a single processing device and may encompassmultiple processing devices. Similarly, the controller 160 is notlimited to a single controller but may encompass multiple controllers.

The memory 504 includes one or more disks, tape drives, or solid-statedrives, and may be used as an over-flow data storage device, to storeprograms when such programs are selected for execution, and to storeinstructions and data that are read during program execution. The memory504 may be volatile or non-volatile and may include ROM, RAM, ternarycontent-addressable memory (TCAM), dynamic random-access memory (DRAM),and static random-access memory (SRAM). The memory 504 is operable tostore the pre-requisite criteria 162, initial sensor measurements 164,current, or validation, measurements 166, validation criteria 168,thresholds 506, and operational history information 508. Thepre-requisite criteria 162, initial sensor measurements 164, currentmeasurements 166, and validation criteria 168 are described above withrespect to FIGS. 1 and 4. The thresholds 506 generally include anythresholds used to perform the function described in this disclosure(e.g., a minimum or threshold time during which one or more of thecompressors 106 a,b should be inactive before validation is performed).The operational history information 508 generally includes informationused to determine whether validation should be performed on a givensensor 114 a,b, 118 a,b, 132 a,b, 136 a,b or set of sensors 114 a,b, 118a,b, 132 a,b, 136 a,b. For instance, the operational history information508 may include a record of times during which one or more of thecompressors 106 a,b, other components of the HVAC system have beenactive, previous validation successes and failures for the sensors 114a,b, 118 a,b, 132 a,b, 136 a,b, and the like.

The I/O interface 506 is configured to communicate data and signals withother devices. For example, the I/O interface 506 may be configured tocommunicate electrical signals with components of the HVAC system 100including the compressors 106 a,b, the expansion valves 122 a,b, theblower 144, sensors 114 a,b, 118 a,b, 132 a,b, 136 a,b, 148, 150, 152,and the thermostat 154. The I/O interface 506 may provide and/orreceive, for example, compressor speed signals blower speed signals,temperature signals, relative humidity signals, thermostat calls,temperature setpoints, environmental conditions, and an operating modestatus for the HVAC system 100 and send electrical signals to thecomponents of the HVAC system 100. The I/O interface 506 may includeports or terminals for establishing signal communications between thecontroller 160 and other devices. The I/O interface 506 may beconfigured to enable wired and/or wireless communications.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods might beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

To aid the Patent Office, and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants notethat they do not intend any of the appended claims to invoke 35 U.S.C. §112(f) as it exists on the date of filing hereof unless the words “meansfor” or “step for” are explicitly used in the particular claim.

What is claimed is:
 1. A heating, ventilation, and air conditioning(HVAC) system comprising a first compressor circuit, the firstcompressor circuit comprising: a compressor configured to compressrefrigerant flowing through the HVAC system; a condenser configured toreceive compressed refrigerant and allow heat to transfer from thecompressed refrigerant to a first flow of air, thereby cooling thecompressed refrigerant; an evaporator configured to receive the cooledrefrigerant and allow heat to transfer from a second flow of air to thecooled refrigerant; a sensor configured to measure a value associatedwith the refrigerant in the condenser or the evaporator; and acontroller communicatively coupled to the compressor and the sensor, thecontroller configured to: determine, based on an operational history thecompressor, that pre-requisite criteria are satisfied for entering asensor validation mode, the prerequisite criteria comprising arequirement that the compressor has been inactive for at least a minimumtime; in response to determining the pre-requisite criteria aresatisfied, determine, using the sensor, an initial sensor measurementvalue; following determining the initial sensor measurement value,operate the compressor according to a sensor-validation mode, whereinoperating according to the sensor-validation mode comprises operatingthe compressor at a maximum recommended capacity, wherein operatingaccording to the sensor-validation mode further comprises over-riding adefault cubic feet per meter per tonnage of cooling (CFM/ton) setting ofthe HVAC system and operating according to a decreased CFM/ton setting;following operating the compressor according to the sensor-validationmode for at least a minimum time, determine, using the sensor, a currentsensor measurement value; determine whether validation criteria aresatisfied for the current sensor value, based on a comparison of thecurrent sensor measurement value to the initial sensor measurementvalue; in response to determining that the validation criteria aresatisfied, determine that the sensor is validated; and in response todetermining that the validation criteria are not satisfied, determinethat the sensor failed validation.
 2. The HVAC system of claim 1, theHVAC system further comprising a second compressor circuit, thecompressor circuit comprising: a second compressor, a second condenser,a second evaporator, and a sensor configured to measure a valueassociated with refrigerant in the second condenser or the secondevaporator; the controller coupled to the second compressor and thesecond sensor, the controller further configured to: determine a firsttime since a most recent validation of the sensor of the firstcompressor circuit; determine a second time since a most recentvalidation of the second sensor of the second compressor circuit;determine the second time is greater than the first time; and inresponse to determining the second time is greater than the first time,determine that the second sensor should be evaluated for validation. 3.The HVAC system of claim 1, wherein operating according to thesensor-validation mode further comprises one or both of: decreasing aspeed of an outdoor fan configured to provide the first flow of airacross the condenser; and closing dampers of an economizer of the HVACsystem such that outdoor air is not included in the second flow of airacross the evaporator.
 4. The HVAC system of claim 1, the controllerfurther configured to, prior to determining the initial sensormeasurement value, determine that one or more secondary pre-requisitecriteria are satisfied, the secondary pre-requisite criteria comprisinga requirement that cooling is needed in a space being conditioned by theHVAC system, a requirement that a current time is within a predefinedsensor validation time interval, and a requirement that the compressoris due for validation.
 5. The HVAC system of claim 1, the evaporator ofthe first compressor circuit is an intertwined evaporator, wherein thesensor is located in or on the intertwined evaporator; and thecontroller further configured to, prior to determining the initialsensor measurement value, determine that all compressors of the HVACsystem have been inactive for at least the minimum time.
 6. The HVACsystem of claim 1, the controller further configured to determinewhether the validation criteria are satisfied for the current sensorvalue by: determining a difference between the current measurement valueand the initial measurement value; determining whether the difference iswithin a predefined range of difference values, wherein the predefinedrange corresponds to range of values previously determined for thesensor being validated; responsive to determining the difference iswithin the predefined range, determining that the validation criteriaare satisfied; and responsive to determining the difference is notwithin the predefined range, determining that the validation criteriaare not satisfied.
 7. The HVAC system of claim 1, the controller furtherconfigured to: determine that one or more secondary sensor validationcriteria are satisfied, the secondary sensor validation criteriacomprising one or both of a requirement that an outdoor temperature iswithin a first predetermined temperature range and a requirement that areturn air temperature is within a second predetermined temperaturerange; and in response to determining that at least one secondary sensorvalidation criteria is not satisfied, determine that the sensor failedvalidation.
 8. A method of operating a heating, ventilation, and airconditioning (HVAC) system, the method comprising: determining, based onan operational history of a compressor of the HVAC system, thatpre-requisite criteria are satisfied for entering a sensor validationmode, the prerequisite criteria comprising a requirement that thecompressor has been inactive for at least a minimum time; in response todetermining the pre-requisite criteria are satisfied, determining aninitial sensor measurement value, based on a signal from a sensor of afirst compressor circuit of the HVAC system; following determining theinitial sensor measurement value, operating the compressor according toa sensor-validation mode, wherein operating according to thesensor-validation mode comprises operating the compressor at a maximumrecommended capacity, wherein operating according to thesensor-validation mode further comprises over-riding a default cubicfeet per meter per tonnage of cooling (CFM/ton) setting of the HVACsystem and operating according to a decreased CFM/ton setting; followingoperating the compressor according to the sensor-validation mode for atleast a minimum time, determining a current sensor measurement value;determining whether validation criteria are satisfied for the currentsensor value, based on a comparison of the current sensor measurementvalue to the initial sensor measurement value; in response todetermining that the validation criteria are satisfied, determining thatthe sensor is validated; and in response to determining that thevalidation criteria are not satisfied, determining that the sensorfailed validation.
 9. The method of claim 8, further comprising:determining a first time since a most recent validation of the sensor ofthe first compressor circuit of the HVAC system; determining a secondtime since a most recent validation of a second sensor of a secondcompressor circuit of the HVAC system; determining that the second timeis greater than the first time; and in response to determining thesecond time is greater than the first time, determining that the secondsensor should be evaluated for validation.
 10. The method of claim 8,wherein operating according to the sensor-validation mode furthercomprises one or both of: decreasing a speed of an outdoor fanconfigured to provide the first flow of air across the condenser; andclosing dampers of an economizer of the HVAC system such that outdoorair is not included in the second flow of air across the evaporator. 11.The method of claim 8, further comprising, prior to determining theinitial sensor measurement value, determining that one or more secondarypre-requisite criteria are satisfied, the secondary pre-requisitecriteria comprising a requirement that cooling is needed in a spacebeing conditioned by the HVAC system, a requirement that a current timeis within a predefined sensor validation time interval, and arequirement that the compressor is due for validation.
 12. The method ofclaim 8, wherein the sensor is located in or on an intertwinedevaporator; and the method further comprising prior to determining theinitial sensor measurement value, determining that all compressors ofthe HVAC system have been inactive for at least the minimum time. 13.The method of claim 8, further comprising determining whether thevalidation criteria are satisfied for the current sensor value by:determining a difference between the current measurement value and theinitial measurement value; determining whether the difference is withina predefined range of difference values, wherein the predefined rangecorresponds to range of values previously determined for the sensorbeing validated; responsive to determining the difference is within thepredefined range, determining that the validation criteria aresatisfied; and responsive to determining the difference is not withinthe predefined range, determining that the validation criteria are notsatisfied.
 14. The method of claim 8, further comprising: determiningthat one or more secondary sensor validation criteria are satisfied, thesecondary sensor validation criteria comprising one or both of arequirement that an outdoor temperature is within a first predeterminedtemperature range and a requirement that a return air temperature iswithin a second predetermined temperature range; and in response todetermining that at least one secondary sensor validation criteria isnot satisfied, determining that the sensor failed validation.
 15. Acontroller of a heating, ventilation, and air conditioning (HVAC)system, the controller comprising a processor configured to: determine,based on an operational history a compressor of the HVAC system, thatpre-requisite criteria are satisfied for entering a sensor validationmode, the prerequisite criteria comprising a requirement that thecompressor has been inactive for at least a minimum time; in response todetermining the pre-requisite criteria are satisfied, determine, using asensor of a first compressor circuit of the HVAC system, an initialsensor measurement value; following determining the initial sensormeasurement value, operate the compressor according to asensor-validation mode, wherein operating according to thesensor-validation mode comprises operating under cooling conditions,wherein operating according to the sensor-validation mode furthercomprises over-riding a default cubic feet per meter per tonnage ofcooling (CFM/ton) setting of the HVAC system and operating according toa decreased CFM/ton setting; following operating the compressoraccording to the sensor-validation mode for at least a minimum time,determine, using the sensor, a current sensor measurement value;determine whether validation criteria are satisfied for the currentsensor value, based on a comparison of the current sensor measurementvalue to the initial sensor measurement value; in response todetermining that the validation criteria are satisfied, determine thatthe sensor is validated; and in response to determining that thevalidation criteria are not satisfied, determine that the sensor failedvalidation.
 16. The controller of claim 15, further configured to:determine a first time since a most recent validation of the sensor ofthe first compressor circuit; determine a second time since a mostrecent validation of the second sensor of the second compressor circuit;determine the second time is greater than the first time; and inresponse to determining the second time is greater than the first time,determine that the second sensor should be evaluated for validation. 17.The controller of claim 15, wherein operating according to thesensor-validation mode further comprises one or more of: decreasing aspeed of an outdoor fan configured to provide a first flow of air acrossa condenser of the HVAC system; and closing dampers of an economizer ofthe HVAC system such that outdoor air is not included in a second flowof air across an evaporator of the HVAC system.
 18. The controller ofclaim 15, further configured to, prior to determining the initial sensormeasurement value, determine that one or more secondary pre-requisitecriteria are satisfied, the secondary pre-requisite criteria comprisinga requirement that cooling is needed in a space being conditioned by theHVAC system, a requirement that a current time is within a predefinedsensor validation time interval, and a requirement that the compressoris due for validation.